1. Field of the Invention
The present invention relates to acoustic and thermal insulation. More particularly, the present invention relates to thermal and acoustic insulation blankets for use in thermally and acoustically insulating exhaust systems in the pipeline industry, more particularly adapted to insulating compound curvatures such as turbines and turbochargers, where normally multiple blocks would be utilized in the insulating of the entire curvature surface.
2. General Background
In the early development of this invention, prototype insulation blankets consisted of a ceramic fiber core encased in a fiberglass logging fabric. Anchors, washers and stitching staples were made of galvanized steel. Since the fiberglass logging fabric was not waterproof, the prototype blankets were not installed for outdoor application without additional weather proofing. This additional weather proofing required coating the fiberglass logging cloth with a mastic weather proofing compound, usually a polyvinyl acrylic mastic. The mastic application, however, hindered removal and replacement of the blanket. Experimental runs of the prototype blanket were made utilizing an outer covering of fiberglass logging fabric laminated to aluminum foil. The foil surface was intended to act as a weatherproofing agent, however, temperature limitation and weather-related failures often resulted.
A silicone treated fiberglass cloth then became available in the late 1970's and it was immediately put into use as the water and oil resistant jacket for the prototype insulation blankets. In early 1980, a random inspection of the prototype blankets indicated that the galvanized anchors were beginning to rust in chemical plant service; therefore in early 1980, stainless steel lacing anchors and washers were used exclusively.
In an effort to upgrade the quality of the ceramic fiber core portion of the experimental blanket, a core with a higher percentage alumina silica content was utilized. This ceramic fiber was rated at 2400.degree. F. and offered less permanent linear change about 1600.degree. F., but there was difficulty in maintaining a consistent core thickness. Consistent thickness was finally achieved by using a ceramic fiber core having the same alumina-silica content, but only a 2300.degree. F. rating and four pounds per cubic foot density. Additionally, in an effort to enhance the incombustible properties of the insulation blankets, a new silicone rubber treated fiberglass cloth was utilized in late 1981 and is presently utilized in the apparatus of the present invention. Finally, an effort to improve the prototype blankets led to using a 6 pounds per cubic foot 2300.degree. F. rated ceramic fiber blanket with a higher compressive strength and lower thermal conductivity.
The apparatus of the present invention, as it is disclosed in its final preferred embodiment, has a multitude of uses in the marine, industrial and offshore industries. It can be used in the acoustic and thermal insulation of bolts, flanges, valves, elbows, tees, reducers, laterals, closures, steam turbines, gas turbines, tubrocharges, and other engine exhaust systems and high pressure gas lines. The use of these thermal insulation blankets would usually obviate the outdated methods of conventional block insulation and, as stated earlier, would be particularly useful in insulating compound curvatures. In the past these compound curvatures were insulated with one or more layers of block insulation, the finished surface then being built up with a layer of insulating finishing cement reinforced with hex mesh or steel lathe. A final cover of asbestos lagging cloth saturated with sizing adhesive would then be used to cover it. There are several patents which address the use of an insulation type of system for curvature objects, the most pertinent being as follows:
U.S. Pat. No. 3,000,433 issued to R. K. Kemper entitled "Thermal Insulation For A Pipe" which teaches the use of a method of insulating a pipe or the like with the use of a thick layer of flexible porous insulating material of low compressor strength, on the upper side of the horizontal pipe, the material being in the form of slabs or blocks. On the upper side of the pipe, there would be a loose fibrous highly efficient insulating material, there being radial spacers extending between the layers and an overall covering of metal.
U.S. Pat. No. 3,724,491 issued to Knudsen, et al entitled "Removable Valve Insulation And Cover", teaches the use of an insulating shelf or valve made up of a plurality of sections which mate together about the valve, each section having an inner and outer skin with insulation material between the skin.
U.S. Pat. No. 4,207,918 entitled "Insulation Jacket" teaches the use of an insulation jacket for use as a valve cover, with the jacket having a body portion with a central section and two lateral sections. Each of the lateral sections would comprise an inboard and outboard belt with the belts extending along each of the lateral sections. The insulation jacket is comprised of fiberglass cloth fabric coated with a silicone rubber coated so as to render it resistant to water and outside conditions.
U.S. Pat. No. 4,201,247 issued to Shannon entitled "Fibrous Product And Method And Apparatus For Producing Same" would teach the use of a fibrous product having amorphous glass fibers and mineral fibers and a method for forming or processing blends or laminations of such fibers to produce several composite fibrous end products used as fire-rated acoustical tile and ceiling board, etc.
U.S. Pat. No. 4,077,491 issued to Hankel entitled "Acoustical Composite" discloses an improved acoustical material for use as a lining material in association with noise generating machinery generally comprising two woven fiberglass layers and an intermediate non-woven fibrous layer to form a composite which has acoustical flow resistance.
U.S. Pat. No. 3,527,258 issued to A. S. Farr entitled "Flexible Tubing" teaches a helical coil of wire with connector members secured to each end of the wire having an inner layer of insulating material and an outer vapor barrier material.